Disproved the myth about the first animal on Earth
American researchers have found that sponges are the oldest animals on Earth, despite the well-established scientific ideas. Analysis of the genomes of different living beings showed that the first was a ctenophores (Ctenophora). The article was published in the journal Nature Ecology & Evolution, the newspaper reports ScienceAlert.
Marine sponges (Porifera) — multicellular invertebrate organisms — are one of the oldest forms of life. Due to the simple structure of their bodies was believed that they are ancestors of all other animals on Earth. However, some studies showed that actually the most ancient animals are ctenophores more complex than sponges, creatures.
New Study Says We Were Wrong About Sea Sponges Being the World’s First Animals https://t.co/rob4ZIKDAt
— ScienceAlert (@ScienceAlert) 11 APR 2017
This view was challenged, as other biologists did not find its confirmation, and the question of who was the first of these two invertebrates, remained open.
To assess the genetic differences that show how people related to others, using the matrix of genetic distances. For example, in the analysis of the gene And the scientists compare it with the genes B and C and determine which pairs are most similar to each other. The smaller the similarity, the greater the genetic distance, and thus, the less related genes. Based on thus obtained results, line up the phylogenetic tree — diagram that reflects evolutionary relationships between organisms.
In the new work, scientists analyzed the genomes of different animals to measure phylogenetic signal which shows which of the two types closer to the third. To do this, they evaluated the similarity level of thousands of genes belonging to 58 species of vertebrates, 103 species of plants and 86 species of yeast. The researchers came to the conclusion that, if we take for comparison a small group of genes, it can lead to different results. This explains why various research works which tried to identify the first animal that appears contradicted each other.
Given this, the researchers with high precision has identified the most ancient branch of animals. To do this, they tested three different hypotheses: the comb jellies appeared before sponges, and other animals; sponges appeared before the ctenophores and other animals; sponges with ctenophores appeared later than the other animals. The researchers measured the phylogenetic signal and found that a large proportion of the analyzed genes supports the first hypothesis.